This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:    3GPP third generation partnership project    BS base station    BW bandwidth    CA carrier aggregation    CC component carrier    CQI channel quality indicator    DL downlink (Node B/eNB towards UE)    eNB E-UTRAN Node B (evolved Node B)    EPC evolved packet core    Ês received energy per resource element (power normalized to the subcarrier spacing) during the useful part of the symbol, i.e., excluding the cyclic prefix, at the UE antenna connector    E-UTRAN evolved UTRAN (LTE)    FDMA frequency division multiple access    HSPA high speed packet access    IMTA international mobile telecommunications association    IoT received power spectral density of the total noise and interference for a certain resource element (power integrated over the resource element and normalized to the subcarrier spacing) as measured at the UE antenna connector    ITU-R international telecommunication union-radiocommunication sector    LTE long term evolution of UTRAN (E-UTRAN)    LTE-A LTE advanced    MAC medium access control (layer 2, L2)    MM/MME mobility management/mobility management entity    Node B base station    OFDMA orthogonal frequency division multiple access    O&M operations and maintenance    PCC primary component carrier    PDCP packet data convergence protocol    PDCCH physical downlink control channel    PDSCH physical downlink shared channel    PHY physical (layer 1, L1)    Rel release    RLC radio link control    RLF radio link failure    RRC radio resource control    RRH remote radio head    RRM radio resource management    RSRP reference signal received power    RSRQ reference signal received quality    RSSI received signal strength indicator    SC-FDMA single carrier, frequency division multiple access    SCC secondary component carrier    SGW serving gateway    UE user equipment, such as a mobile station, mobile node or mobile terminal    UL uplink (UE towards Node B/eNB)    UTRAN universal terrestrial radio access network
One modern communication system is known as evolved UTRAN (E-UTRAN, also referred to as UTRAN-LTE or as E-UTRA). In this system the DL access technique is OFDMA, and the UL access technique is SC-FDMA.
One specification of interest is 3GPP TS 36.300, V8.11.0 (2009-12), “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Access Network (EUTRAN); Overall description; Stage 2 (Release 8).” This system may be referred to for convenience as LTE Rel-8. In general, the set of specifications given generally as 3GPP TS 36.xyz (e.g., 36.211, 36.311, 36.312, etc.) may be seen as describing the Release 8 LTE system. More recently, Release 9 versions of at least some of these specifications have been published including 3GPP TS 36.300, V9.1.0 (2009-9).
FIG. 1A reproduces FIG. 4.1 of 3GPP TS 36.300 V8.11.0, and shows the overall architecture of the EUTRAN system (Rel-8). The E-UTRAN system includes eNBs, providing the E-UTRAN user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE (not shown). The eNBs are interconnected with each other by means of an X2 interface. The eNBs are also connected by means of an S1 interface to an EPC, more specifically to a MME by means of a S1 MME interface and to an S-GW by means of a S1 interface (MME/S-GW 4). The S1 interface supports a many-to-many relationship between MMEs/S-GWs and eNBs.
The eNB hosts the following functions:                functions for RRM: RRC, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both UL and DL (scheduling);        IP header compression and encryption of the user data stream;        selection of a MME at UE attachment;        routing of User Plane data towards the EPC (MME/S-GW);        scheduling and transmission of paging messages (originated from the MME);        scheduling and transmission of broadcast information (originated from the MME or O&M); and        a measurement and measurement reporting configuration for mobility and scheduling.        
Of particular interest herein are the further releases of 3GPP LTE (e.g., LTE Rel-10) targeted towards future IMTA systems, referred to herein for convenience simply as LTE-Advanced (LTE-A). Reference in this regard may be made to 3GPP TR 36.913, V9.0.0 (2009-12), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Requirements for Further Advancements for E-UTRA (LTE-Advanced) (Release 9). Reference can also be made to 3GPP TR 36.912 V9.2.0 (2010-03) Technical Report 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Feasibility study for Further Advancements for E-UTRA (LTE-Advanced) (Release 9).
A goal of LTE-A is to provide significantly enhanced services by means of higher data rates and lower latency with reduced cost. LTE-A is directed toward extending and optimizing the 3GPP LTE Rel-8 radio access technologies to provide higher data rates at lower cost. LTE-A will be a more optimized radio system fulfilling the ITU-R requirements for IMT-Advanced while keeping the backward compatibility with LTE Rel-8.
As specified in 3GPP TR 36.913, LTE-A should operate in spectrum allocations of different sizes, including wider spectrum allocations than those of LTE Rel-8 (e.g., up to 100 MHz) to achieve the peak data rate of 100 Mbit/s for high mobility and 1 Gbit/s for low mobility. It has been agreed that carrier aggregation (CA) is to be considered for LTE-A in order to support bandwidths larger than 20 MHz. Carrier aggregation, where two or more component carriers (CCs) are aggregated, is considered for LTE-A in order to support transmission bandwidths larger than 20 MHz. The carrier aggregation could be contiguous or non-contiguous. This technique, as a bandwidth extension, can provide significant gains in terms of peak data rate and cell throughput as compared to non-aggregated operation as in LTE Rel-8.
A terminal may simultaneously receive one or multiple component carriers depending on its capabilities. A LTE-A terminal with reception capability beyond 20 MHz can simultaneously receive transmissions on multiple component carriers. An LTE Rel-8 terminal can receive transmissions on a single component carrier only, provided that the structure of the component carrier follows the Rel-8 specifications. Moreover, it is required that LTE-A should be backwards compatible with Rel-8 LTE in the sense that a Rel-8 LTE terminal should be operable in the LTE-A system, and that a LTE-A terminal should be operable in a Rel-8 LTE system.
FIG. 1B shows an example of the carrier aggregation, where M Rel-8 component carriers are combined together to form a total MHRel-8 BW (e.g. 5 H 20 MHz=100 MHz given M=5). Rel-8 terminals receive/transmit on one component carrier, whereas LTE-A terminals may receive/transmit on multiple component carriers simultaneously to achieve higher (wider) bandwidths.
In CA multiple cells (or UL/DL CCs) can be aggregated for multi-carrier transmission/reception. It has been agreed that the configuration of the DL/UL CC for CA is to be performed using RRC signaling between the eNB and the UE. One UL and DL CC are configured for a primary CC (PCC), while other CCs are referred to as secondary CCs (SCC).
It has also been agreed that in order to enable UE battery savings a separate MAC level activation/deactivation mechanism is to be introduced for the DL SCC and also potentially for the UL SCC. However, according to the current agreement there is no need to have a separate activation mechanism for the UL SCC.